1. Field of the Invention
The present invention relates to a heavy-duty shear which is adapted to be attached to a backhoe and, more particularly, the present invention relates to a piercing tip for a heavy-duty shear.
2. Prior Art
Heavy-duty shears are mounted on backhoes and powered by hydraulic cylinders for the efficient handling and shearing of scrap, generally metal scrap. The scrap is sheared into usable sizes. For example, in dismantling an industrial building, metal scrap in the form of pipes of various diameters and lengths, structural beams, such as I-beams, channels, angles and the like, sheet metal and sheet plates must all be efficiently handled and severed by the shears. Shears are additionally utilized for reducing automobile and truck frames, railroad cars and the like. The shears must be able to move and cut the metal scrap pieces regardless of the size or shape of the individual scrap piece and without any significant wedging or biting action of the workpieces relative to the shears, or other damage to the shears.
U.S. Pat. No. 4,198,747 generally discloses a hydraulic shear for a backhoe. FIGS. 4 and 5 illustrate the typical operation for a hydraulic shear of this design. The hydraulic shear does not include hardened inserts along the moveable jaw, however, cutting inserts are disclosed in many later patents. U.S. Pat. No. 4,519,135 to LaBounty, for example, discloses a metal demolition shear in which the upper jaw 14 includes a shear blade 21 having hardened cutting inserts 24 and 25 defining shear edges 24.1 and 25.1. FIG. 2 of the LaBounty '135 patent illustrates the shearing edges. My prior U.S. Pat. Nos. 4,403,431 and 4,450,625 both disclose material handling and shearing attachment for a backhoe which utilizes a hook-shaped cutting blade. The hook-shaped cutting blade is used to grasp, hold, pull and/or lift beams, pipes, cables and the like to be sheared back to the cutting edges of the shear. U.S. Pat. No. 4,543,719 to Pardoe discloses a shear attachment for a backhoe in which the upper pivotal jaw includes a pair of replaceable cutting blades 22. U.S. Pat. No. 4,719,975 to LaBounty discloses a shear utilized for the demolition of concrete. The shear includes hardened insert bars 72 and 74 in the respective fixed and moveable jaws 50 and 54 to form the cutting edges of the shear. These patents do not include a separate piercing action by a piercing tip or insert. Additionally, these patents do not include a continuous cutting edge along the upper jaw of the moveable blade extending from the end of the jaw to the pivot point. Without a piercing tip, these shears are not efficient at handling metal scrap which extends beyond the length of the jaw.
Some of the prior art shears are adapted to operate on a workpiece which is longer than the jaw length of the shear. When these shears are working on a workpiece which is longer than the jaw length of the shears, the forwardmost portion of the movable blade is used to pierce into the workpiece such that the forward portion of the blade forms a piercing tip. This allows the cutting edge sections behind the piercing tip to more easily sever the remaining portions of the workpiece. The prior art heavy-duty shear designs which incorporate a piercing tip are limited in that they are not designed for the most efficient piercing operation of the workpiece.
U.S. Pat. No. 4,776,093 to Gross discloses metal demolition shears utilizing removable blade inserts. A moveable boot tip 91 surrounds the projecting tip 31 of the upper jaw 19. The boot tip is mounted by countersunk, recessed bolts on one side of the upper jaw and acts as a wear plate during operation. The use of a boot completely surrounding the leading edge of the upper jaw limits the construction of the width of the upper jaw relative to the spacing of the lower jaw. Specifically, the upper jaw must be dimensioned so that the upper jaw together with the surrounding boot tip is sized to fit through the slot in the lower jaw opening. My prior U.S. Pat. Nos. 4,670,983 and 4,897,921 disclose similar heavy-duty shears to the present invention. The metal cutting shears include a moveable plate having a v-shaped cutting configuration with a piercing tip insert at the leading edge of the moveable blade. One drawback of these designs is that the piercing tip does not extend to the remaining blade inserts. This construction can result in undue wear on the jaw face of the moveable blade. The above patents do not provide for the most efficient design of the piercing tip or for a coordination of the design of the piercing tip with the type of scrap product which is primarily to be cut by the shears.
It is an object of the present invention to overcome the aforementioned drawbacks of the prior art. It is another object of the present invention to provide efficient, replaceable piercing tips for a metal cutting shear. It is a further object of the present invention to provide a shear designed to operate effectively in conjunction with a piercing tip.